What's up with the other members of the Convocation? (Spoilers)

[Veloran]

The aetherial sea isn't the space between the Shards. If it was, souls would just rejoin in the sea as they naturally do after a rejoining. Basically it appears each Shard's Lifestreams are not connected to each other.

[Vyrerus]

The aetherial sea isn't the space between the Shards. If it was, souls would just rejoin in the sea as they naturally do after a rejoining. Basically it appears each Shard's Lifestreams are not connected to each other.

Each Lifestream is attached to the Aetherial Sea. This much is apparent due to Minfilia getting sucked into the Flow teleportation magic that spirits her through the Lifestream to the Aetherial Sea. And it is where Hydaelyn resides and keeps watch on all shards, so yes, it is.

[Iscah]

I'd like to add my hunch that the 12 Ancients following Venat and help summon Hydaelyn are probably the 12 gods of the people of Eorzea. You can see them in the cutscene that immediately follows Anemnesis Anyder.

Whatever is going on, it's more complicated than that. Azem isn't one of those twelve, but got a goddess named after them regardless.

Meanwhile, whether planned or not, Nald'thal seems to equate to Emet-Selch quite neatly. Lord of the Underworld and associated with Gemini, the Twins...

I've wondered if these memories could be triggered with interaction with the missing Midgradsormr children who would have lived through all of these events.

Midgardsormr, Hraesvelgr, Nidhogg and Tiamat lived through all those events too, and they didn't trigger anything in us. There's nothing inherently special about the other dragons just because of that.

While Tenzen being a previous incarnation of Azem is on the table, Ramza is not - his soul is still lingering around the Orbonne Monastery when we go there.

Tenzen's soul was apparently bound up in Koryu's seal, so he can't have been an incarnation either.

Unless of course we're understanding the "one soul per shard" thing wrong and they can all flow freely through the aetherial sea and pop up anywhere, in which case it would be possible for them to be other shards of Azem... but that explanation may be messier in other ways. We still don't understand how the aetherial sea works.

So while we probably could travel to other worlds this way, we'd have to leave our physical body behind to do so. Only the Exarch has managed to circumvent that limitation, both in his initial departure from the Eighth Era to the First and in his subsequent summoning of the WoL from the Source to the First. Even then, his first half-dozen attempts all backfired horribly—The first five attempts ended up pulling the Scions' souls out of their bodies instead, and the sixth attempt left the WoL's comatose body just a few fulms away from Elidibus-Zenos.

While it's arguably no longer a true world but a void where a world used to be, we did physically go to the World of Darkness prior to that - and using a gate opened by the Crystal Tower to do so. It may be a critical part of the mechanism for the summoning spell, even if Omega's rift powers were also needed for the full solution.

On "messing up the sixth attempt" to summon us, I feel like that one might have been more that it was urgent to get in contact right now and he didn't have time to properly set up the summoning, so he sort of pulled us halfway just to get the message across.

It's also my headcanon that this might have been the actual point where the timelines diverge, and if he hadn't pulled us there and then we would have killed "Zenos" and it would have been a turning point in the battle that eventually led to the cornered Garleans using Black Rose.

[YianKutku]

Meanwhile, whether planned or not, Nald'thal seems to equate to Emet-Selch quite neatly. Lord of the Underworld and associated with Gemini, the Twins...

Nald'Thal (or more specifically Nald) is also the god associated with commerce and trade. Emet-Selch didn't even bother with trade in his empire-building, preferring espionage and conquest instead.

More directly, there isn't any deity in Aldenard nor Othard (we know the Garleans prohibited religion on Ilsabard) that has a name that sounds like "Emet-Selch" (or "Hades"), to the same degree as Azem and Azeyma/Azim.

[Kesey]

Whatever is going on, it's more complicated than that. Azem isn't one of those twelve, but got a goddess named after them regardless.

I think this has been explained as the names like Emet-Selch, Lahabrea, and Azem are the title held by the seat and isn't the real name. Furthermore, if our original Ancient self decided to defect because of Zodiark but then also refused to join Hydaelyn (as told in the cutscenes with Venat) it stands to reason that their copycat convocation (Venat's Hydaelyn convocation) would still use the titles of office for the seats, every easily giving the Azem title to someone new.